Buildings look like they are leaning back in your architecture shots? Don't worry, it's simple to correct...
Within photography circles, there are some basic competencies that we should always get right. And these competencies are so fundamental that getting them wrong can be considered to be cardinal, photography sins.
Missing the focus, blowing highlights or blocking out shadows are errors a competent photographer should never make. And in the world of architectural photography, another fundamental competency exists - correct perspective. And is the one key element that separates the imagery of a skilled architectural photographer from the rest.
The problem with perspective
In order to correctly reproduce vertical lines in a photograph, it is useful to understand what causes the problem.
When you capture an image from a perfectly level position, your vertical lines will be correct (i.e. 90 degrees). In practice, this is almost always impossible. Walk outside and try photographing your house while keeping the camera level. You’ll notice that you can only capture the bottom half.
Here are some examples:
In order to fit the entire house in, you’ll have to tilt the camera upwards. As soon as you tilt the camera upwards, the vertical lines in the image will start to converge towards each other.
The effect of photographing from this perspective is that the building will appear to be leaning backwards.
This is immediately noticeable in architectural scenes and cityscapes, but also impacts natural scenes too. When you point a wide-angle lens upwards to fit in a mountain, it will have an effect of diminishing the height of the mountain.
In order to prevent this from happening, you will need to photograph from the exact vertical mid-point of the subject you’re trying to capture. This is usually impractical or impossible.
Fortunately, for all the times where you cannot get to the vertical mid-point, there are two methods for correcting the perspective.
Here are those two images with the perspective corrected:
Correcting the perspective in-camera
Perspective correction is such a fundamental competency for architectural photographers, that specialist lenses exist for this very purpose.
These lenses are most commonly referred to as tilt-shift lenses, based on the two unique movements that the lens is able to do. To correct the perspective using a tilt shift lens, you will only need to use the shift movement.
A tilt shift lens keeps verticals correct by allowing you to photograph from a level position. Once the camera is level, instead of tilting up like you would with a regular lens, you shift upwards on the lens, all while keeping the camera level.
An example of a good tilt-shift lens is the Canon TS-E 24mm f/3.5L II.
Correcting perspective with software
Modern retouching software has sophisticated tools for correcting perspective. In this example, I will use Lightroom’s perspective correcting tool, but the principle is similar with other software packages.
To correct the perspective using Lightroom, use the panel labelled “Transform”.
To correct vertical lines, four options exist, “Auto”, “Vertical”, “Full” and “Guided”. The first three are one-click options that sometimes work, but for greater accuracy, I tend to use the “Guided” option.
The “Guided” option allows you to draw up to four lines on the image to guide the lines in the image. To correct just the vertical lines, draw a line along the outer vertical lines of the image.
Once two guidelines have been drawn, the perspective of the image will be corrected.
In camera vs software
Tilt-shift lenses are expensive and specifically designed for architectural photography. They offer no zoom functionality and no auto focus. Why would anyone choose to use a tilt shift lens instead of just fixing the perspective in software?
If you’re a professional architectural photographer, in other words, if you’re trading your time for money, the time saved getting in right in camera vs in software adds up quickly. On retouching days, I can go through 30-50 images per day. At only 2 minutes extra per image, that adds up to over an hour and a half saved per day.
In addition, getting it right in camera allows you to see the finished result while you’re still on site. This means you can fine tune your composition to ensure you don’t miss any critical detail. Correcting with software crops off areas of the image and changes the composition. It is difficult to visualise what impact these changes will have while you’re still in the field. That cropping and stretching of the image also degrades image quality, although with modern, high resolution sensors, this is not as critical as it once was.
Finally, photographers are often expected to be able to add video as a service. While it is relatively easy to correct the perspective of a photograph, the same cannot be said about video. It would be very difficult to create architectural videos without a tilt shift lens.
Therefore, if you plan on doing a significant amount of architectural photography work, a tilt shift lens is a worthwhile purchase. If you’re more of a generalist photographer who occasionally photographs architecture, you may be better off correcting perspective in software.